MountaineerTom
LJ Enthusiast, Retired USAF Weapons Loader
Supporting Member
Ride of the Month Winner
Did you install them with the open channel down?
Nevermind, I thought you meant installed the the upper control arms backwards.
Front driveshaft contacting skid plate
- Thread starter ThomasFletch
- Start date
Did you install them with the open channel down?
Nevermind, I thought you meant installed the the upper control arms backwards.
OP
While waiting for my replacement control arm to show up, I started to wonder; What do rear driveshaft vibes feel like? I know the Jeep isn't supposed to ride like a Rolls-Royce or anything, so what should I be looking for? Scouring the forums, people also say that every TJ is different, but how are they different? What does that mean, feel or look like? I've seen people say SYE, adjustable control arms, a MML or Tcase drop to eliminate vibes. I've seen some that say you don't need anything. When driving, I do get vibrations past 70mph, but I don't know if that's because I'm driving a brick into the wind, CA freeways suck, or if it really is the driveshaft vibrating. (I promise I'm not calling you out @Blackjack)
@MountaineerTom, since you have the same setup as me, do you experience any vibration past 70, or installed an SYE and adjustable control arms?
I know I've asked basically this same question 15 times already, so I apologize if this came off as hostile, it was not my intention at all. I am just a bit overwhelmed by all the different answers on here!
MountaineerTom
LJ Enthusiast, Retired USAF Weapons Loader
Supporting Member
Ride of the Month Winner
I don’t get past 70 very often, but the few times I have, I didn’t feel any vibrations. No SYE and stock control arms on my Jeep.
I only drive my Jeep 70 mph when in town, otherwise 80 mph+.
No vibes at any speeds.p.s. CA freeways are the least thing that suck there. Living there should be #1 on the long list.
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No we are not driving Rolls but really there is little reason we can not have a decently smooth drive not counting how aggressive a tire you run.
Angle induced vibes will typically will manifest themselves either during acceleration or deceleration and will feel like you have a rumble. If the pinion is pointed too high the vibes will occur under acceleration and the opposite if the angle is too low. A lot of folks will say everything is good until they get to freeway speeds and they notice a vibe and my guess is the the pinion is still a touch high. These bricks we drive take a fair amount of push to maintain those speeds so the driveshaft is under a pretty substantial load.
Out of balance shafts usually show up in a range of speed say 45-55 and if you are not in that range things seem fine. Loose or worn parts will start at say 25-35 and the vibes never go away.
Also vibes at high speed can be a lot of different things. Bad tires, high speed engine miss, a bad bearing in the trans or tcase (I have a story about that one), lower quality engine/trans mount can all make you think it is the driveshaft.
OP
Well, the second installation has been so far so good. It took some finagling, pictures, and some grinding for clearance. No dents as of now, but I have yet to test it on the local fire roads. Regarding vibes, I think I am good! I truly value your guy's input on that, thank you. The only slightly strange thing that I've noticed is that on hard acceleration there is a quick shudder, and then it's fine. I'm thinking it might be the rear axle slightly moving due to the torque from a strong accelerating start and changing the pinion angle for a split second? If it sounds serious to you guys, I'll make a separate post for it. But for now, I'll try to ignore it.
That sounds correct. You might also notice the shudder or rumble when driving up a steep hill because you’re giving it more power to climb at speed and it’s raising the pinion.
You have asked a couple times about pinion angle. Hope this helps. Tom Woods has a great video on their website, but I don’t know how to attach.
OP
Do you think it would be worth it to install one or is it fine to leave like this?
The TJ has a very short rear drive shaft and I had vibrations with my 2nd lift of 2.5 inches. Your profile says you have a 3.75 inch lift plus a body lift. Too much for stock driveshaft configuration. You can do a T-case drop with spacers or do a SYE. Either will work and I’ve done both. My final resolution for my current 4 inch coils was a Slip Yoke Eliminator for the transfer case, Adams double cardan drive shaft (HD with sealed U-joints), and rear axle adjustable control arms. Study all the past threads and I bet you will learn a lot.
OP
@Hi-Desert Thank you for pointing out that I had put 3.75. I guess in my head, I added my suspension lift and the body lift together for some reason. My actual lift is the OME 2" lift (really 2.5" with the spacers, so I've read) and then the Savvy Offroad 1.25" body lift.
I'm unsure if this would change your opinion, as I know you said you had a lift of 2.5 at one point, but I appreciate your opinion either way! I'm very much reluctant to do the body lift as I know that would be losing ground clearance. Currently, I am looking at the SYE kit and the double cardan driveshaft as well as the rear adjustable control arms to go with it, but I don't know if it is really worth it yet.
When I was looking at my rear-driveshaft, I remembered back when I changed the U-joints that I may have possibly installed it upside down. So, I flipped it around and then went on a test drive on the freeway and around town. Whereas the vibrations from a heavy throttle start were still there, I felt way less vibration on the freeway at 70, to the point where I really do think it was on backwards.